Pyridinylurea N-oxide compounds and agricultural uses

ABSTRACT

Pyridinylurea N-oxides of the formula ##STR1## and acid addition salts thereof; wherein R is cycloalkyl (C 3  -C 8 ), alkenyl (C 3  -C 8 ), or an alkyl (C 1  -C 6 ) group optionally substituted with halogen, hydroxy, cycloalkyl (C 3  -C 8 ) alkoxy (C 1  -C 6 ), dialkyl (C 1  -C 6 )amino or phenyl; R 1  is hydrogen or alkyl (C 1  -C 6 ); R and R 1  together with the nitrogen atom of the NRR 1  group optionally define a nonaromatic heterocycle containing 4 to 6 ring carbon atoms; each X independently is halogen, alkyl (C 1  -C 6 ), haloalkyl (C 1  -C 6 ), alkoxy (C 1  -C 6 ), hydroxy, 2-pyridinyl, alkyl(C 1  -C 6 )thio or alkyl (C 1  -C 6 )sulfonyl; A is 1 to 4; and wherein the NHCONRR 1  group is bonded to the pyridinyl ring in the 3- or 4-position. The compounds are useful in agriculture as plant growth regulators.

TECHNICAL FIELD

This invention concerns certain pyridinylurea N-oxides and their use inagriculture.

Representative of research efforts in the field are the compoundsdisclosed in U.S. Pat. Nos. 4,063,928 (substitutedpyridinyloxy(thio)phenyl acetamides, ureas and urea derivatives),4,193,788 (N-(2-chloro-4-pyridyl)ureas, 4,279,639(N-(2-substituted-4-pyridylureas), 4,308,054 (other pyridyl ureas),3,293,257 and 3,330,641 (pyridyl ureas), and 3,469,965 (ureaderivatives).

SUMMARY OF THE INVENTION

The compounds of the invention are pyridinylurea N-oxides of the formula(I): ##STR2## and acid addition salts thereof; wherein R is cycloalkyl,alkenyl, or an alkyl group optionally substituted with halogen,hydroxyl, alkoxy, cycloalkyl, dialkylamino or phenyl; R¹ is hydrogen oralkyl; R and R¹ together with the nitrogen atom of the NRR¹ groupoptionally define a non-aromatic heterocycle containing 4 to 6 ringcarbon atoms; each X independently is halogen, alkyl, haloalkyl, alkoxy,hydroxy, 2-pyridinyl, alkylthio or alkylsulfonyl; A is 1 to 4; andwherein the NHCONRR¹ group is bonded to the pyridinyl ring in the 3- or4-position.

The compounds have utility in agriculture including plant regulatoryactivity in terms of one or more of stunting, dessication, axillarygrowth stimulation, nastic response, growth stimulation, defoliation,intumescence, negative root geotropism, darker green basal leaves, leafalteration and retardation of senescence.

DETAILED DESCRIPTION

In formula I, the carbon chains in R, R¹ and X may be straight orbranched and except for alkenyl and cycloalkyl may contain 1 to 6 carbonatoms. The preferred carbon range is 1 to 4 carbon atoms, for all groupsother than alkenyl and cycloalkyl, from the standpoint of ease ofsynthesis. The alkenyl and cycloalkyl groups may each contain 3 to 8carbon atoms. Typical alkenyl groups are propenyl and butenyl. "Halogen"means chloro, bromo, fluoro and iodo, preferably in that order. Thehaloalkyl of the R and X groups may contain more than one halogen atom,either the same halogen or mixed halogens such as di- ortrifluoromethyl, di- or trichloromethyl, and the like. N-heterocyclesdefined by NRR¹ are non-aromatic groups which nevertheless may containsome unsaturation, such as pyrrolidinyl, 3-pyrrolinyl and piperidinyl.

When X in formula I is halogen, such as chloro, and the NHCONRR¹ groupis in the 4-position on the pyridinyl ring, plant regulator activity ofthe compounds is greater if the halogen is in the 2- and/or 6-positionson the pyridinyl ring. Similarly, when the NHCONRR¹ group is in the3-position on the pyridinyl ring, plant regulator activity is greater ifthe halogen is in one or both of the 4- and 5-positions. Preferredcompounds of formula I are those wherein R is propyl, 1-methylethyl,butyl (straight or branched), cyclopentyl or 2-chloroethyl, R¹ ishydrogen, X is 2-chloro or 2-bromo and the urea group is in the4-position on the pyridinyl ring.

The acid addition salts of the compounds of formula I include organicand inorganic salts such as the hydrochlorides, sulfates, phosphates,citrates and tartrates. Preferably, but not necessarily, the salts arewater soluble or water dispersible.

The compounds of formula I wherein R is other than cycloalkyl areprepared in a generally known manner by oxidizing pyridine to theN-oxide with hydrogen peroxide, nitrating with a mixture of fumingsulfuric and nitric acids, reducing the nitro group to amino byhyrogenation over palladium on carbon, and coupling with an isocyanate(R--NCO). For preparation of compounds of formula I wherein R is alkylor cycloalkyl and/or R¹ is alkyl, the amino intermediate is reacted withphenyl chloroformate to form a phenyl N-(pyridinyl-N oxide)carbamateintermediate which is then reacted with an alkyl amine (mono or di) or acycloalkyl amine to form the corresponding monoalkyl, dialkyl orcycloalkyl product. Alternatively, an aminopyridine intermediate isprepared from the corresponding ester via the Curtius reaction. Theaminopyridine is then reacted with an appropriate isocyanate (R--NCO) toform the pyridinyl urea. The pyridinyl urea is oxidized to the N-oxideproduct by reaction with m-chloroperoxybenzoic acid. The reactions areconducted in appropriate organic solvents with appropriate pressure andtemperature controls. The work-up and isolation procedures areconventional.

Further details of synthesis are given in the representative examplesbelow. Table I (appended lists the compounds of the examples andprovides characterizing data for the synthesis examples and othercompounds of the invention. In compound 36 of Table I, A is 2. In allother compounds of Table I, A is 1.

EXAMPLE 1 Synthesis of N-(2-chloro-4-pyridinyl-Noxide)-N'-(1-methylethyl)urea (Compound No. 7) Step A 2-Chloropyridine-Noxide

A stirred solution of 1656 grams (14.6 moles) of 2-chloropyridine in 4.3liters of glacial acetic acid was warmed to 50° C. and 1.5 liters of 30%hydrogen peroxide was added dropwise. Upon completion of addition thereaction mixture was stirred at 50° C. for 45 hours during which 30%hydrogen peroxide, 500 ml at a time, was added at 5 hours, 16 hours, and22 hours into the stirring time. The reaction mixture was concentratedto one-half volume, diluted with 5 liters of water, and againconcentrated to one-half volume. The mixture was made basic with 1000grams of sodium carbonate, and excess hydrogen peroxide was decomposedby the addition of 400 grams of sodium bisulfite. The mixture wasconcentrated under reduced pressure to a residual solid. The solid wasextracted with two five-liter portions of chloroform. The combinedextracts were dried with magnesium sulfate and filtered. The filtratewas concentrated under reduced pressure to yield 1335 grams of2-chloropyridine-N oxide; m.p. 66°-69° C.

Step B 2-Chloro-4-nitropyidine-N oxide

With stirring, 1.5 liters of concentrated sulfuric acid was cooled to20° C. and 1058 grams (6.06 moles) of 2-chloropyridine-N oxide was addedportionwise during a 5 hour period. The reaction mixture temperature wasmaintained at 5°-10° C. and 590 ml of 90% nitric acid was addeddropwise. Upon completion of addition the reaction mixture was heated to80° C. and the source of heat was removed. The exothermic reactioncaused the reaction mixture temperature to rise to 115° C. During a onehour period the reaction mixture temperature fell from 115° C. to 100°C., where it was maintained for four hours with an external heat source.The reaction mixture was cooled then poured into 12 liters of ice. Theresultant solid was collected by filtration and washed three times bysuspension in three one-liter portions of water. The solid was dried toyield 725 grams of 2-chloro-4-nitropyridine-N oxide. The mother liquorand washes were combined and extracted with four one-liter portions ofchloroform. The combined extracts were dried with potassium carbonateand filtered. The filtrate was concentrated under under reduced pressureto a residual solid. The solid was triturated in 65 ml of 2-propanol toyield an additional 94.2 grams of 2-chloro-4-nitropyridine-N oxide.

Step C 4-Amino-2-chloropyridine

A stirred solution of 696 grams (3.99 moles) of2-chloro-4-nitropyridine-N oxide, 700 ml of acetic acid, 700 ml ofn-butyl ether, and 5.6 liters of water was cooled to 0°-5° C. and 1400grams (25.1 mole) of iron was added in one portion. Upon completion ofaddition the reaction mixture temperature rose to 90° C. during a 30minute period despite efforts to cool the reaction mixture with an icebath. The increase in temperature was accompanied by foaming. After thefoaming subsided and the reaction mixture temperature began to fall, theice bath was removed and the reaction mixture stirred without coolingfor one hour. The reaction mixture was cooled and made basic with asolution of 1400 grams of potassium hydroxide in 1.4 liters of water.The thick slurry was filtered through diatomaceous earth, and 100 gramsof solid potassium hydroxide was added to the filtrate. The filtrate wasextracted with one liter of diethyl ether. The filter cake was suspendedin three liters of hot ethanol and filtered. The procedure was repeatedtwice more using two two-liter portions of hot ethyl acetate. Theextracts were combined and concentrated under reduced pressure to asolid residue. The solid was dissolved in two liters of diethyl etherand the solution diluted with 2.5 liters of petroleum ether. Theresultant solid was collected by filtration and dried to yield 419.6grams of 4-amino-2-chloropyridine; m.p. 93°-95° C.

Step D N-(2-chloro-4-pyridinyl)-N'-(1-methylethyl)urea

A solution of 2.6 grams (0.0203 mole) of 4-amino-2-chloropyridine, 0.53gram of (0.005 mole) 1,4-diazabicyclo[2.2.2]octane (DABCO), and 3.9 ml(0.0305 mole) of (1-methylethyl) isocyanate in 20 ml of drydimethylformamide was stirred at ambient temperature for five days. Thedimethylformamide was removed under reduced pressure. The residue wastaken up in 20 ml of ethanol and this was removed under reducedpressure. The procedure was repeated a second time using an additional20 ml of ethanol. The residual oil was dried under reduced pressure atambient temperature for 16 hours, then under reduced pressure at 60° C.for one hour. The resultant solid was triturated in hot water. Themixture was allowed to cool to ambient temperature then placed in arefrigerator where it stood for 60 hours. The solid was collected byfiltration, washed with water and dried under reduced pressure for threehours at 40°-50° C. The yield ofN-(2-chloro-4-pyridinyl)-N'-(1-methylethyl)urea was 4.1 grams, m.p.142°-146.5° C. The nmr spectrum was consistent with the proposedstructure.

Step E N-(2-chloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)urea

A solution of 1.2 grams (0.0055 mole) ofN-(2-chloro-4-pyridinyl)-N'-(1-methylethyl)urea, 2.0 grams (0.01 mole)of m-chloroperoxybenzoic acid in 45 ml of methylene chloride and 100 mlof diethyl ether was stirred at ambient temperature for 24 hours, thenat 40° C. for an additional 24 hours. A solid precipitate was collectedby filtration. The solid was analyzed by thin layer chromatography (TLC)and was found to be a mixture of product and starting material. Thesolid was dissolved in 250 ml of methylene chloride and a small amountof methanol. The solution was evaporated onto 25 ml of silica gel. Uponcompletion of evaporation the silica gel-solid combination was driedunder reduced pressure at 40° C. for three hours. The silica gel-solidcombination was placed on a column of 200 ml of silica gel. The columnwas eluted with 500 ml of diethyl ether to remove excessm-chloroperoxybenzoic acid, then with one liter of 10%methanol-methylene chloride, followed by 500 ml of 15%methanol-methylene chloride to separate the product from its impurities.The appropriate fractions were combined and concentrated under reducedpressure to yield 0.82 gram of N-(2-chloro-4-pyridinyl-Noxide)-N'-(1-methylethyl)urea, m.p. 170° C., dec. The nmr spectrum wasconsistent with the proposed structure.

EXAMPLE 2 Synthesis of N-(2,6-dichloro-4-pyridinyl-N oxide)N'-(1-methylethyl)urea (Compound No. 36) Step A Methyl(2,6-dichloropyridine-N oxide)-4-carboxylate

A stirred solution of 25.0 grams (0.12 mole) of methyl(2,6-dichloropyridine)-4-carboxylate in 250 ml of trifluoroacetic acidwas warmed to 76° C. and 8 ml of 30% hydrogen peroxide was added. Thereaction mixture was stirred for 30 minutes and an additional 6 ml of30% hydrogen peroxide was added, followed by five more aliquots of 6 mleach of 30% hydrogen peroxide during a four hour period. Upon completionof addition the heating of the reaction mixture at 76° C. was continuedfor 3.5 hours, then it was allowed to cool to ambient temperature whereit stood for 16 hours. The reaction mixture was concentrated underreduced pressure to a residue. The residue was slurried in water and themixture was concentrated under reduced pressure to a residue. Theresidue was recrystallized from acetone to yield 19 grams of methyl(2,6-dichloropyridine-N oxide)-4-carboxylate as a solid. The nmrspectrum was consistent with the proposed structure.

Step B (1,1-Dimethylethyl) N-(2,6-dichloro-4-pyridinyl-N oxide)carbamate

This compound was prepared from methyl (2,6-dichloropyridine-Noxide)-4-carboxylate via a Curtius reaction, analogous to that describedby M. T. Garcia-Lopez et al., J. Het. Chem., 19, 233, 1982.

Step C 4-Amino-2,6-dichloropyridine-N oxide

A solution of 2.3 grams (0.008 mole) of (1,1-dimethylethyl)N-(2,6-dichloro-4-pyridinyl-N oxide)carbamate in 5 ml of trifluoroaceticacid was stirred at ambient temperature for one hour. The excesstrifluoroacetic acid was removed under reduced pressure. The residue wastaken up in toluene and the mixture concentrated under reduced pressureto a residue. The procedure was repeated using a second aliquot oftoluene. The residue was taken up in toluene a third time and stirredwith 2-3 ml of aqueous saturated sodium bicarbonate. The mixture wasfiltered to collect, when dried, 0.9 gram of4-amino-2,6-dichloropyridine-N oxide as a solid. The nmr spectrum wasconsistent with the proposed structure.

Step D N-(2,6-dichloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)urea

This compound was prepared in the manner of Example 1, Step D, using 0.9gram (0.005 mole) of 4-amino-2,6-dichloropyridine-N oxide, 0.2 gram(0.002 mole) of 1,4-diazabicyclo[2.2.2]octane (DABCO) and 0.6 ml (0.006mole) of (1-methylethyl) isocyanate in 4 ml of dry dimethylformamide.The yield of N-(2,6-dichloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)ureawas 0.7 gram; m.p. 208°-210° C., dec. The nmr spectrum was consistentwith the proposed structure.

EXAMPLE 3 Synthesis of N-(2-methylthio-4-pyridinyl-Noxide)-N'-(1-methylethyl)urea (Compound No. 41)

To a stirred solution of 3.3 grams (0.0144 mole) ofN-(2-chloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)urea (prepared as inExample 1) in 20 ml of dimethylformamide was added, in one portion, 2.5grams (0.0359 mole) of sodium methanethiolate. The reaction mixture waswarmed to 50°-55° C. where it stirred for one day. The reaction mixturewas concentrated and the residue dried under reduced pressure at 60° C.The residue was dissolved in a minimum of 10% methanolmethylene chlorideand placed on a column of silica gel. Elution was accomplished with 5%and 15% methanol-methylene chloride. The appropriate fractions werecombined and concentrated under reduced pressure to yield 2.3 grams ofN-(2-methylthio-4-pyridinyl-N oxide)-N'-(1-methylethyl)urea; m.p.222°-224° C. The nmr spectrum was consistent with the proposedstructure.

EXAMPLE 4 Synthesis of N-[2-(2-pyridinyl)-4-pyridinyl-Noxide]N'-(1-methylethyl)urea (Compound No. 45) Step A 2-(2-pyridinyl)pyridine-N oxide

A solution of 25.0 grams (0.160 mole) of 2,2'-bipyridine and 33.1 grams(0.163 mole) of 85% pure m-chloroperoxybenzoic acid in 500 ml ofmethylene chloride was stirred at ambient temperature for 16 hours. TLCanalysis of the reaction mixture indicated it to be a mixture ofstarting materials, the mono- and the di-oxides. One-third of thereaction mixture was placed on a column of silica gel. The column waseluted with diethyl ether to collect starting materials, and with 10%methanol-methylene chloride to collect the mono-oxide. The appropriatefractions were combined and concentrated under reduced pressure to yield8.0 grams of 2-(2-pyridinyl)pyridine-N oxide, as an oil which solidifiedon standing. The remaining two-thirds of the reaction mixture wassubjected to column chromatography as described above to yield anadditional 13.9 grams of 2-(2-pyridinyl)pyridine-N oxide. The nmrspectra were consistent with the proposed structure.

Step B 4-Nitro-2-(2-pyridinyl)pyridine-N oxide

This compound was prepared in the manner of Example 1, Step B using 13.7grams (0.080 mole) of 2-(2-pyridinyl)pyridine-N oxide, 85 ml ofconcentrated sulfuric acid, and 60 ml of concentrated fuming nitricacid. The yield of 4-nitro-2-(2-pyridinyl)pyridine-N oxide was 10.5grams; m.p. 178°-183° C. The nmr spectrum was consistent with theproposed structure.

Step C 4-Amino-2-(2-pyridinyl)pyridine-N oxide

A suspension of 2.6 grams (0.012 mole) of4-nitro-2-(2-pyridinyl)pyridine-N oxide and 0.42 gram of 10% palladiumon charcoal in 10 ml of water and 200 ml of ethanol was hydrogenatedusing a Parr hydrogenator. Upon completion of hydrogenation the reactionmixture was purged with nitrogen gas for one hour, then concentratedunder reduced pressure to a residual solid. The solid was trituratedwith 200 ml of water. The mixture was filtered and the filter cakewashed with water. The combined filtrate and wash were concentratedunder reduced pressure to a residue. The residue was taken up in 30 mlof ethanol and concentrated under reduced pressure. This procedure wasrepeated three additional times to remove residual water. The residuewas dried under reduced pressure at 60° C. to yield 1.9 grams of4-amino-2-(2-pyridinyl)pyridine-N oxide as a solid. The nmr spectrum wasconsistent with the proposed structure.

Step D N-[2-(2-pyridinyl)-4-pyridinyl-N oxide]N'-(1-methylethyl)urea

This compound was prepared in the manner of Example 1, Step D, using 0.9gram (0.0048 mole) of 4-amino-2-(2-pyridinyl)pyridine-N oxide, 0.28 gram(0.002 mole) of 1,4-diazabicyclo[2.2.2]octane (DABCO), 1.0 ml (0.010mole) of (1-methyethyl) isocyanate in 20 ml of dimethylformamide. Theyield of N-[2-(2-pyridinyl)-4-pyridinyl-N oxide]-N'-(1-methylethyl)ureawas 0.5 gram; m.p. 100° C. The nmr spectrum was consistent with theproposed structure.

Plant Regulator Utility

Plant growth regulators are used to modify plants by changing the rateor pattern, or both, of their response to internal and external factorsthat govern all stages of development from germination throughvegatative growth, reproductive development, maturity and senescence. Inaddition, harvest aids, ripening agents, and chemicals for post-harvestpreservation may be considered plant regulators. Plant regulators may beapplied directly to a plant or to the soil in the vicinity of the plantto alter its life processes or morphological structure in somebeneficial way, for example to enhance yield, improve quality,facilitate harvesting or otherwise advantageously modify growth anddevelopment. Such beneficial effects may include, but are not limitedto, root initiation; set, development, ripening and abscission offruits; plant size and shape; suppression of lodging; control ofaxillary buds and lateral shoots; metabolism regulation, includingsenscence; breaking or enforcing dormancy in seeds, buds, and storageorgans; promotion or delay of flowering; defoliation; desiccation; andgrowth promotion under stress. Sometimes the same compound can bothinhibit and promote growth, depending upon the rate of application.

The pyridinylurea N-oxides of the invention exhibit various forms ofplant regulator activity when tested in vitro and in whole plant assaysas described more particularly hereinbelow. Briefly, such activity isapparent in preemergence and post-emergence plant response screens on avariety of plants, particularly soybean and cotton, where morphologicalresponses include stunting, axillary growth stimulation, nasticresponse, defoliation, darker green basal leaves, and some herbicidalactivity. In antisenescence assays, compounds of the invention causeretention of chlorophyll in excised wheat leaves and in soybean leavesand pods, while reducing abscission, thus indicating ability to retardsenescence.

The plant regulators of this invention are effectively employed as plantregulators in a number of broad-leafed and grain crops, for example,soybean, lima bean, wheat, rice, corn, sorghum, and cotton, and turfgrasses.

The plant regulator compounds, like most agricultural chemicals, aregenerally not applied full strength, but are formulated withagriculturally acceptable carriers or extenders (diluents) normallyemployed for facilitating the dispersion of active ingredients andvarious additives, and optionally with other active ingredients,recognizing that the formulation and mode of application of the activecomponent may affect the activity of the material. The present compoundsmay be applied, for example, as powders or liquids, the choice ofapplication varying with the plant species and environmental factorspresent at the particular locus of application. Thus, the compounds maybe formulated as emulsifiable concentrates, wettable powders, flowableformulations, solutions, dispersions, suspensions and the like.

A typical formulation may vary widely in concentration of the activeingredient depending on the particular agent used, the additives andcarriers used, other active ingredients, and the desired mode ofapplication. With due consideration of these factors, the activeingredient of a typical formulation may, for example, be suitablypresent at a concentration of from about 0.5% up to about 99.5% byweight of the formulation. Substantially inactive ingredients such asadjuvants, diluents, and carriers may comprise from about 99.5% byweight to as low as about 0.5% by weight of the formulation. Surfaceactive agents, if employed in the formulation, may be present at variousconcentrations, suitably in the range of 1 to 30% by weight. Providedbelow is a general description of representative formulations which maybe employed for dispersion of the plant regulators of the presentinvention.

Emulsifiable concentrates (EC's) are homogeneous liquid compositions,usually containing the active ingredient dissolved in a liquid carrier.Commonly used liquid carriers include xylene, heavy aromatic naphthas,isophorone, and other nonvolatile or slightly volatile organic solvents.For application, these concentrates are dispersed in water, or otherliquid vehicle, forming an emulsion, and are normally applied as a sprayto the area to be treated. The concentration of the essential activeingredient in EC's may vary according to the manner in which thecomposition is to be applied, but, in general, is in the range of 0.5 to95%, frequently 10 to 80%, by weight of active ingredient, with theremaining 99.5% to 5% being surfactant and liquid carrier.

The following are specific examples of emulsifiable concentrateformulations suitable for use in the present invention:

    ______________________________________                                        Formulation 1:        % by Wt.                                                ______________________________________                                        Active ingredient     53.01                                                   Blend of alkylbenzenesulfonate salt                                                                 6.00                                                    and polyoxyethylene ethers                                                    Epoxidized soybean oil                                                                              1.00                                                    Xylene                39.99                                                   Total                 100.00                                                  ______________________________________                                    

    ______________________________________                                        Formulation 2:                                                                ______________________________________                                        Active ingredient     10.00                                                   Blend of alkylbenzenesulfonate salt                                                                 4.00                                                    and polyoxyethylene ethers                                                    Xylene                86.00                                                   Total                 100.00                                                  ______________________________________                                    

Wettable powders are in the form of finely divided particles whichdisperse readily in water or other liquid vehicles. The wettable powderis ultimately applied to the plant as a dry dust or a dispersion inwater or other liquid. Typical carriers for wettable powders includefuller's earth, kaolin clays, silicas, and other highly absorbent oradsorbent inorganic diluents. The concentration of active ingredient inwettable powders is dependent upon physical properties of the activeingredient and the absorbency characteristics of the carrier. Liquidsand low melting solids (mp<100° C.) are suitably formulated in theconcentration range of 5 to 50% by weight, usually from 10 to 30%; highmelting solids (mp>100° C.) being formulated in the range of 5 to 95% byweight, usually 50 to 85%. An agriculturally acceptable carrier ordiluent, frequently including a small amount of a surfactant tofacilitate wetting, dispersion and suspension, accounts for the balanceof the formulation.

The following are specific examples of wettable powder formulationssuitable for use in the present invention:

    ______________________________________                                        Formulation 3:        % by Wt.                                                ______________________________________                                        Active ingredient     25.00                                                   Base:                 75.00                                                   2% Sodium ligninsulfonate                                                     2% Sodium alkylnaphthalenesulfonate                                           96% Attapulgite clay                                                          Total                 100.00                                                  ______________________________________                                    

    ______________________________________                                        Formulation 4:                                                                ______________________________________                                        Active ingredient    90.00                                                    Dioctyl sodium sulfosuccinate                                                                      0.10                                                     Synthetic fine silica                                                                              9.90                                                     Total                100.00                                                   ______________________________________                                    

    ______________________________________                                        Formulation 5:                                                                ______________________________________                                        Active ingredient     20.00                                                   Sodium alkylnaphthalenesulfonate                                                                    1.00                                                    Sodium ligninsulfonate                                                                              4.00                                                    Attapulgite clay      75.00                                                   Total                 100.00                                                  ______________________________________                                    

    ______________________________________                                        Formulation 6:           % by Wt.                                             ______________________________________                                        Active ingredient        25.00                                                Base:                    75.00                                                96% hydrated aluminum magnesium silicate                                      2% powdered sodium ligninsulfonate                                            2% powdered anionic sodium alkyl-                                             naphthalenesulfonate                                                          Total                    100.00                                               ______________________________________                                    

Flowable formulations are similar to EC's except that the activeingredient is suspended in a liquid carrier, generally water. Flowables,like EC's , may include a small amount of a surfactant, and containactive ingredient in the range of 0.5 to 95%, frequently from 10 to 50%,by weight of the composition. For application, flowables may be dilutedin water or other liquid vehicle, and are normally applied as a spray tothe area to be treated.

The following are specific examples of flowable formulations suitablefor use in the present invention:

    ______________________________________                                        Formulation 7:         % by Wt.                                               ______________________________________                                        Active ingredient      46.00                                                  Colloidal magnesium aluminum silicate                                                                0.40                                                   Sodium alkylnaphthalenesulfonate                                                                     2.00                                                   Paraformaldehyde       0.10                                                   Water                  41.42                                                  Propylene glycol       7.50                                                   Acetylinic alcohols    2.50                                                   Xanthan gum            0.08                                                   Total                  100.00                                                 ______________________________________                                    

    ______________________________________                                        Formulation 8:        % by Wt.                                                ______________________________________                                        Active ingredient     45.00                                                   Water                 48.50                                                   Purified smectite clay                                                                              2.00                                                    Xanthan gum           0.50                                                    Sodium alkylnaphthalenesulfonate                                                                    1.00                                                    Acetylinic alcohols   3.00                                                    Total                 100.00                                                  ______________________________________                                    

Typical wetting, dispersing or emulsifying agents used in agriculturalformulations include, but are not limited to, the alkyl and alkylarylsulfonates and sulfates and their sodium salts; alkylaryl polyetheralcohols; sulfated higher alcohols; polyethylene oxides; sulfonatedanimal and vegetable oils, sulfonated petroleum oils; fatty acid estersof polyhydric alcohols and the ethylene oxide addition products of suchesters; and the addition product of long-chain mercaptans and ethyleneoxide. Many other types of useful surface-active agents are available incommerce. The surface-active agent, when used, normally comprises from 1to 15% by weight of the composition.

Other useful formulations include simple solutions or suspensions of theactive ingredient in a relatively non-volatile solvent such as water,corn oil, kerosene, propylene glycol, or other suitable solvents. Thistype of formulation is particularly useful for ultra low volumeapplication.

The following illustrate specific suspensions which are suitable for usein the present invention:

    ______________________________________                                        Formulation 9-Oil Suspension:                                                                     % by Wt.                                                  ______________________________________                                        Active ingredient   5.42                                                      Emulsifier A        5.00                                                      Emulsifier B        5.00                                                      Suspending agent    5.00                                                      Carrier-diluent     79.58                                                     Total               100.00                                                    ______________________________________                                    

In formulation 9 Emulsifier A is the anionic free acid of a complexorganic ester sold under the trademark and designation "GAFAC RE-410."Emulsifier B is a formulated nonionic concentrate sold under thetrademark and designation "FloMo 200-4." The suspending agent is abentonite clay sold under the trademark and designation "Bentone 34."The carrier-diluent is a mineral oil of viscosity 60 SUS sold under thetrademrk and designation "Sunspray 6N Oil."

    ______________________________________                                        Formulation 10-Aqueous Suspension                                                                   % by Wt.                                                ______________________________________                                        Active ingredient     4.92                                                    Antimicrobial agent   0.05                                                    Foam suppressant      0.10                                                    Surfactant C          2.60                                                    Surfactant D          0.40                                                    Thickener             0.35                                                    Suspending agent      0.45                                                    Propylene glycol      6.00                                                    Water                 85.13                                                   Total                 100.00                                                  ______________________________________                                    

The anitmicrobial agent is sodium o-phenylphenate tetrahydrate soldunder the trademark and designation "Dowacide A". The foam suppressantis a water dilutable silicone emulsion sold under the trademark anddesignation "Dow Corning AF". Surfactant C is a nonionic paste of acondensate of ethylene oxide with a hydrophobic base formed bycondensing propylene oxide with propylene glycol, sold under thetrademark and designation "Pluronic P-84." Surfactant D is an anionicliquid comprising the sodium salt of a complex organic phosphate ester,sold under the trademark and designation "GAFAC LO-529." The thickeneris a xantham gum sold under the trademark and designation "Kelzan-M".The suspending agent is a colloidal magnesium aluminum silicate soldunder the trademark and designation "Veegum."

The concentration of the compound in use dilution is normally in therange of about 2% to about 0.1%. Many variations of spraying and dustingcompositions in the art may be used by substituting or adding a compoundof this invention into compositions known or apparent to the art.

The compositions may be formulated and applied with other suitableactive ingredients, including nematicides, insecticides, acaricides,fungicides, other plant regulators, herbicides, fertilizers and otheragricultural chemicals.

In applying the foregoing chemicals, an effective growth regulatingamount of the active ingredient must be employed. While the applicationrate will vary widely depending on the choice of compound, theformulation and mode of application, the plant species being treated,the planting density and the growth response desired, a suitable userate may be in the range of 0.01 to 10 kg/hectare, preferably 0.05 toabout 5 kg/hectare. The compounds may be applied directly to a plant orto the soil or other locus of the plant.

The compounds of the invention were tested for plant regulator activity,first in a whole plant response screen and then in excised wheat leafand soybean whole plant antisenescence tests.

Plant Response Screen

In this assay the test compounds are applied as water-acetone (1:1)solutions, containing 0.5% v/v sorbitan monolaurate solubilizer, at arate equivalent to 8.0 kg/ha, preemergently to planted seeds of testplants and postemergently to foliage of test plants. The test plantswere soybean, cotton, corn, wheat, field bindweed, morningglory,velvetleaf, barnyardgrass, green foxtail and johnsongrass.

All of the test compounds exhibited various forms and degrees of plantregulator activity although not against all of the plants and to thesame extent in each case. Generally, the test compounds were more activewhen applied postemergently. The soybean and cotton plants wereparticularly responsive as evidenced by one or more stunting, axillarygrowth stimulation, nastic response, defoliation, and darker green basalleaves. Morphological responses observed were stem strengthening ingrasses, intumescence, leaf alteration and growth stimulation in theform of larger leaf area and/or internode distance. Some herbicidalactivity was exhibited at the exceptionally high application rate of thetest.

Wheat Leaf Antisenescence

1. Initial Test

In this test leaves were excised from wheat seedlings (Triticum aestivumcv. Prodax), weighed and placed in vials containing solutions of testcompound in water-acetone (1:1) at concentrations of 25 ppm and 2.5 ppm.Wheat leaves were similarly placed in vials containing only deionizedwater, as controls. After four days of incubation at 30° C. in the dark,the test vials were examined visually and given a numeric rating of 0(color similar to color of the leaves in the control vials) or 1 (moregreen than the leaves in the control vials). The control leaves hadyellowed, indicating loss of chlorophyll. The test results, set forth inTable II (appended), show that compounds 3-7, 13, 26 and 36 causedretention of chlorophyll at both 25 ppm and 2.5 ppm as compared with thecontrol and that compounds 2, 8-12, 14, 16-20, 24, 25, 27-29, 31, 35,38, 41, 45 and 54 were active at 25 ppm. The apparent inactivity of theremaining compounds in Table II may be caused by limited solubility inthe water-acetone test solvent.

2. Chlorophyll Retention--Senescence Inhibition (SI₅₀)

Compounds of the invention were tested for their ability to retain thechlorophyll in freshly excised wheat leaves as compared with frozenwheat leaf controls which, theoretically, retain 100% of theirchlorophyll. In the test, excised wheat leaves were weighed and placedin vials of water-acetone (1:1) solutions of test compounds atconcentrations ranging from 10⁻⁵ to 10⁻⁹ molar. Vials containing theleaves in water alone were used as controls. After 4 days incubation at30° C. in the dark, the chlorophyll content of the excised leaves wasdetermined by extracting the leaves with methanol or other solvent. Theabsorbances of the chlorophyll-containing extracts were determinedspectrophotometrically at 652 nm and converted to micrograms ofchlorophyll/gram of fresh leaf weight for test vials and controls by theformula ##EQU1## The calculated results were then divided by themicrograms of chlorophyll/gram fresh weight of the frozen leaf controland the result multiplied by 100 to give percent of chlorophyll retainedas compared with the frozen wheat leaf control. The percent chlorophyllretained in the wheat leaves by the various concentrations of testchemical was plotted against the negative log of the concentration. Fromthe resulting graph, the negative log of the concentration that wouldretain 50% of the chlorophyll (SI₅₀) was determined. The greater theSI₅₀ value, the more active the test chemical as a senescence inhibitor.

The results are given in Table III (appended) for averages of threereplicates from which it will be seen that all of the test compoundscaused some retention of chlorophyll, the average SI₅₀ value being 5.4.Compound 36 has SI₅₀ values ranging from 6.1 to 7.1 and averaging 6.7,making it the most active compound of the test.

Soybean Utility Test

Compounds of the invention were sprayed onto the foliage of soybean testplants at rates of 2.0, 0.50, and 0.125 kg/ha. The test compounds weresprayed as water-acetone (1:1) solutions containing 2% sorbitanmonolaurate emulsifier. The soybean test plants were at the beginningseed stage at the time of spraying.

Approximately 15 days post-treatment, the leaves and pods of the soybeantest plants were inspected for senescence. Leaf and pod senescence wasmeasured using a rating scale of 0-5, 0 indicating leaf and podabscission and 5 being 100% green leaves and pods. The soybean testplants were inspected periodically up to 43 days. At each inspection theleaf and pod senescence was measured using the aforementioned rating.Graphs were prepared for each test chemical in which the mean leafsenescence ratings were plotted against the corresponding dayspost-treatment. A second set of graphs was prepared in which the meanpod senescence ratings were plotted against the corresponding dayspost-treatment. Leaf and pod senescence ratings vs the correspondingdays post-treatment for the untreated control were plotted on these samegraphs. Using the graphs, the number of days delay in reaching 50% leafsenescence (leaf senescence rating=2.5) for each test chemical, ascompared to the untreated control, was determined. The process wasrepeated with the mean pod senescence ratings to determine the number ofdays delay in reaching 50% pod senescence (2.5) for each test chemical.

Table IV (appended) gives the results from which it will be seen thatcompounds 7 and 36 delayed both leaf and pod senescence. Compound 7caused the longest delay in leaf senescence (16 days at 2.0 kg/ha)whereas compound 36 caused the longest delay in pod senescence (7 daysat 1.0 kg/ha).

                                      TABLE I                                     __________________________________________________________________________     ##STR3##                                                                     Cmpd.                                               Empirical Formula/        No.  R            R.sup.1                                                                             X       Name                m.p./b.p.                 __________________________________________________________________________     1   CH.sub.3     H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.7 H.sub.8                                                               ClN.sub.3 O.sub.2                                         N'129 methylurea    S(150-152°                                                             C.)                        2   C.sub.2 H.sub.5                                                                            H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.8 H.sub.10                                                              ClN.sub.3 O.sub.2                                         N'ethylurea         S(137-138°                                                             C.)                        3   CH.sub.2 CH.sub.2 Cl                                                                       H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.8 H.sub.9                                                               Cl.sub.2 N.sub.3                                                              O.sub.2                                                   N'(2-chloroethyl)urea                                                                             S(151-153°                                                             C.)                        4   CH.sub.2 CF.sub.3                                                                          H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.8 H.sub.7                                                               ClF.sub.3 N.sub.3                                                             O.sub.2                                                   N'(2,2,2-trifluoroethyl)urea                                                                      S(186-187°                                                             C.)                        5   C.sub.3 H.sub.7                                                                            H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.9 H.sub.12                                                              ClN.sub.3 O.sub.2                                         N'propylurea        S(145-147° C.,                                                         dec)                       6*  CH(CH.sub.3).sub.2                                                                         H     2-Cl    N(2-chloro-3-pyridinyl-N                                                                          C.sub.9 H.sub.12                                                              ClN.sub.3 O.sub.2                                         N'(1-methylethyl)urea                          7   CH(CH.sub.3).sub.2                                                                         H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.9 H.sub.12                                                              ClN.sub.3 O.sub.2                                         N'(1-methylethyl)urea                                                                             S(170° C.,                                                             dec)                       8   CH.sub.2 CH.sub.2 CH.sub.2 Cl                                                              H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.9 H.sub.11                                                              Cl.sub.2 N.sub.3                                                              O.sub.2                                                   N'(3-chloropropyl)urea                                                                            S(131-139°                                                             C.)                        9   C.sub.4 H.sub.9                                                                            H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'butylurea         S(70-82° C.)       10.sup.(1)                                                                         CH(CH.sub.3)C.sub.2 H.sub.5                                                                H     2-Cl    (±)-N(2-chloro-4-pyridinyl-N                                                                   C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.2                                         oxide)-N'(1-methylpropyl)urea                                                                     S(169-172°                                                             C.)                       11.sup. (2)                                                                        CH(CH.sub.3)C.sub.2 H.sub.5                                                                H     2-Cl    (+)-N(2-chloro-4-pyridinyl-N                                                                      C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.2                                         oxide)-N'(1-methylpropyl)urea                                                                     S(176-179°                                                             C.)                       12.sup.(2)                                                                         CH(CH.sub.3)C.sub.2 H.sub.5                                                                H     2-Cl    (-)-N(2-chloro-4-pyridinyl-N                                                                      C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'(1-methylpropyl)urea                                                                            S(176-179° C.,                                                         dec)                      13   CH.sub.2 CH(CH.sub.3).sub.2                                                                H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'(2-methylpropyl)urea                                                                            S(140-143°                                                             C.)                       14   C(CH.sub.3).sub.3                                                                          H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'(1,1-dimethylethyl)urea                                                                         S(164-166° C.,                                                         dec)                      15   C.sub.5 H.sub.11                                                                           H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'pentylurea        S(134-137° C.,                                                         dec)                      16.sup.(1)                                                                         CH(CH.sub.3)C.sub.3 H.sub.7                                                                H     2-Cl    (±)-N(2-chloro-4-pyridinyl-N                                                                   C.sub.11 H.sub.16                                                             ClN.sub.3 O.sub.2                                         oxide)-N'(1-methylbutyl)urea                                                                      S(156-157°                                                             C.)                       17.sup.(1)                                                                         CH.sub.2 CH(CH.sub.3)C.sub.2 H.sub.5                                                       H     2-Cl    (±)-N(2-chloro-4-pyridinyl-N                                                                   C.sub.11 H.sub.16                                                             ClN.sub.3 O                                               oxide)-N'(2-methylbutyl)urea                                                                      S(134-137° C.,                                                         dec)                      18   CH.sub.2 CH.sub.2 CH(CH.sub.3).sub.2                                                       H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'(3-methylbutyl)urea                                                                             S(141-144° C.,                                                         dec)                      19   C(CH.sub.3).sub.2 C.sub.2 H.sub.5                                                          H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'(1,1-dimethylpropyl)urea                                                                        S(169-170° C.,                                                         dec)                      20   CH.sub.2 C(CH.sub.3).sub.3                                                                 H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'(2,2-dimethylpropyl)urea                                                                        S(150-154° C.,                                                         dec)                      21   C.sub.6 H.sub.13                                                                           H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.12 H.sub.18                                                             ClN.sub.3 O.sub.2                                         N'hexylurea         S(53-61° C.)       22   C.sub.8 H.sub.17                                                                           H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.14 H.sub.22                                                             ClN.sub.3 O.sub.2                                         N'octylurea         S(-)                      23   C(CH.sub.3).sub.2 CH.sub.2 C(CH.sub.3).sub.2 CH.sub.3                                      H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.14 H.sub.22                                                             ClN.sub.3 O.sub.2                                         N'(1,1,3,3-tetramethylbutyl)urea                                                                  S(157-159° C.,                                                         dec)                      24   cyclopropylmethyl                                                                          H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.12                                                             ClN.sub.3 O.sub.2                                         N'(cyclopropylmethyl)urea                                                                         S(163-165° C.,                                                         dec)                      25   cyclobutyl   H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.12                                                             ClN.sub.3 O.sub.2                                         N'cyclobutylurea    S(176-177° C.,                                                         dec)                      26   cyclopentyl  H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'cyclopentylurea   S(183-184° C.,                                                         dec)                      27   cyclohexyl   H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.12 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'cyclohexylurea    S(176-177.5°                                                           C., dec)                  28   cycloheptyl  H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.13 H.sub.18                                                             ClN.sub.3 O.sub.2                                         N'cycloheptylurea   S(174-175° C.,                                                         dec)                      29   phenylmethyl H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.13 H.sub.12                                                             ClN.sub.3 O.sub.2                                         N'(phenylmethyl)urea                                                                              S(169-171°                                                             C.)                       30.sup.(1)                                                                         1-phenylethyl                                                                              H     2-Cl    (±)-N(2-chloro-4-pyridinyl-N                                                                   C.sub.14 H.sub.14                                                             ClN.sub.3 O.sub.2                                         (1-phenylethyl)urea S(182-183°                                                             C.)                       31.sup.(3)                                                                         1-phenylethyl                                                                              H     2-Cl    (+)-N(2-chloro-4-pyridinyl-N                                                                      C.sub.14 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'(1-phenylethyl)urea                                                                             S(137-139° C.,                                                         dec)                      32.sup.(4)                                                                         1-phenylethyl                                                                              H     2-Cl    (-)-N(2-chloro-4-pyridinyl-N                                                                      C.sub.14 H.sub.14                                                             ClN.sub.3 O.sub.2                                         N'(1-phenylethyl)urea                         33*  CH.sub.3     H     6-OC.sub.4 H.sub.9                                                                    N(6-butoxy-3-pyridinyl-N                                                                          C.sub.11 H.sub.17                                                             N.sub.3 O.sub.3                                           N'methylurea                                  34*  CH(CH.sub.3).sub.2                                                                         H     6-Cl    N(6-chloro-3-pyridinyl-N                                                                          C.sub.9 H.sub.12                                                              ClN.sub.3 O.sub.2                                         N'(1-methylethyl)urea                                                                             S(238-240° C.,                                                         dec)                      35   CH(CH.sub.3).sub.2                                                                         H     2-Br    N(2-bromo-4-pyridinyl-N                                                                           C.sub.9 H.sub.12                                                              BrN.sub.3 O.sub.2                                         N'(1-methylethyl)urea                                                                             S(159-161° C.,                                                         dec)                      36   CH(CH.sub.3).sub.2                                                                         H     2,6-dichloro                                                                          N(2,6-dichloro-4-pyridinyl-N                                                                      C.sub.9 H.sub.11                                                              Cl.sub.2 N.sub.3                                                              O.sub.2                                                   oxide)-N'(1-methylethyl)urea                                                                      S(208-210°                                                             C.)                       37*  CH(CH.sub.3).sub.2                                                                         H     6-OCH.sub.3                                                                           N(6-methoxy-3-pyridinyl-N                                                                         C.sub.10 H.sub.15                                                             N.sub.3 O.sub.3                                           N'(1-methylethyl)urea                                                                             S(163- 165°                                                            C.)                       38   CH(CH.sub.3).sub.2                                                                         H     2-OCH.sub.3                                                                           N(2-methoxy-4-pyridinyl-N                                                                         C.sub.10 H.sub.15                                                             N.sub.3 O.sub.3                                           N'(1-methylethyl)urea                                                                             S(186-188° C.,                                                         dec)                      39   CH(CH.sub.3).sub.2                                                                         H     2-OC.sub.3 H.sub.7                                                                    N(2-propoxy-4-pyridinyl-N                                                                         C.sub.12 H.sub.19                                                             N.sub.3 O.sub.3                                           N'(1-methylethyl)urea                                                                             S(154-156° C.,                                                         dec)                      40*  CH(CH.sub.3).sub.2 *                                                                       H     6-OC.sub.4 H.sub.9                                                                    N(6-butoxy-3-pyridinyl-N                                                                          C.sub.13 H.sub.21                                                             N.sub.3 O.sub.3                                           N'(1-methylethyl)urea                                                                             S(190-191° C.,                                                         dec)                      41   CH(CH.sub.3).sub.2                                                                         H     2-SCH.sub.3                                                                           N(2-methylthio-4-pyridinyl-N                                                                      C.sub.10 H.sub.15                                                             N.sub.3 O.sub.2 S                                         N'(1-methylethyl)urea                                                                             S(222-224° C.,                                                         dec)                      42   CH(CH.sub.3).sub.2                                                                         H     2-S(O).sub.2 CH.sub.3                                                                 N(2-methylsulfonyl-4-pyridinyl-N                                                                  C.sub.10 H.sub.15                                                             N.sub.3 O.sub.4 S                                         oxide)-N'(1-methylethyl)urea                                                                      S(223-224° C.,                                                         dec)                      43   CH(CH.sub.3).sub.2                                                                         H     2-N(CH.sub.3).sub.2                                                                   N(2-dimethylamino-4-pyridinyl-N                                                                   C.sub.11 H.sub.18                                                             N.sub.4 O.sub.2                                           oxide)-N'(1-methylethyl)urea                                                                      S(190-191° C.,                                                         dec)                      44.sup.(6)                                                                         CH(CH.sub.3).sub.2.HCl                                                                     H     2-OH.sup.(5)                                                                          N(2-hydroxy-4-pyridinyl-N                                                                         C.sub.9 H.sub.14                                                              ClN.sub.3 O.sub.3                                         oxide)-N'(1-methylethyl)urea                                                                      S(164-165° C.,                                                         dec)                                                      hydrochloride                                 45   CH(CH.sub.3).sub.2                                                                         H     2-(2-pyridinyl)                                                                       N[2-(2-pyridinyl)-4-pyridinyl-N                                                                   C.sub.14 H.sub.16                                                             N.sub.4 O.sub.2                                           oxide]-N'(1-methylethyl)urea                                                                      S(100° C.)         46   (CH.sub.2).sub.2 OCH.sub.3                                                                 H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.9 H.sub.12                                                              ClN.sub.3 O.sub.3                                         N'(2-methoxyethyl)urea                        47   (CH.sub.2).sub.3 OCH.sub.3                                                                 H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.14                                                             ClN.sub.3 O.sub.3                                         N'(3-methoxypropyl)urea                       48   (CH.sub.2).sub.2 N(CH.sub.3).sub.2                                                         H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.15                                                             ClN.sub.4 O.sub.2                                         N'(2-dimethylaminoethyl)urea                  49   (CH.sub.2).sub.3 N(CH.sub.3).sub.2                                                         H     2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.17                                                             ClN.sub.4 O.sub.2                                         N'(3-dimethylaminopropyl)urea                 50   CH(CH.sub.3).sub.2                                                                         H     2-CF.sub.3                                                                            N(2-trifluoromethyl-4-pyridinyl-N                                                                 C.sub.10 H.sub.12                                                             F.sub.3 N.sub.3                                                               O.sub.2                                                   oxide-N'(1-methylethyl)urea                   51   CH(CH.sub.3).sub.2                                                                         H     2-C.sub.3 F.sub.7                                                                     N(2-heptafluoropropyl-4-pyridinyl-                                                                C.sub.12 H.sub.12                                                             F.sub.7 N.sub.3                                                               O.sub.2                                                   N oxide)-N(1-methylethyl)urea                 52   CH.sub.3     C(CH.sub.3).sub.3                                                                   2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'methyl-N'(1,1-dimethylethyl)urea            53   cyclopentyl  CH.sub.3                                                                            2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.12 H.sub.16                                                             ClN.sub.3 O.sub.2                                         N'methyl-N'cyclopentylurea                    54   (CH.sub.2).sub.4   2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.10 H.sub.12                                                             ClN.sub.3 O.sub.2                                         1-pyrrolidine carboxamide                                                                         S(159-160°                                                             C.)                       55   (CH.sub.2).sub.5   2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.11 H.sub.14                                                             ClN.sub.3 O.sub.2                                         1-piperidinecarboxamide                                                                           S(153-155°                                                             C.)                       56   (CH.sub.2).sub.6   2-Cl    N(2-chloro-4-pyridinyl-N                                                                          C.sub.12 H.sub.16                                                             ClN.sub.3 O.sub.2                                         1Hazepine-1-carboxamide                                                                           S(172-173°         __________________________________________________________________________                                                        C.)                        *The urea group (NHCONRR.sup.1) is in the 3position of the pyridine ring.     In all other compounds of Table I the substituted urea is in the              4position.                                                                    .sup.(1) a racemic mixture                                                    .sup.(2) a stereo isomer  configuration uncertain                             .sup.(3) R[+] stereoisomer                                                    .sup.(4) S[-] stereoisomer                                                    .sup.(5) a tautomer                                                           .sup.(6) hydrochloride salt                                              

                  TABLE II                                                        ______________________________________                                        Antisenescence Initial Assay -                                                Wheatleaf Chlorophyll Retention                                                                        Visual Evaluation of                                 Compound                 Wheat Leaves in the                                  Number   Concentration (ppm)                                                                           Test Solutions                                       ______________________________________                                        1        25.0            0                                                             2.5             0                                                    2        25.0            1                                                             2.5             0                                                    3        25.0            1                                                             2.5             1                                                    4        25.0            1                                                             2.5             1                                                    5        25.0            1                                                             2.5             1                                                    6        25.0            1                                                             2.5             1                                                    7        25.0            1                                                             2.5             1                                                    8        25.0            1                                                             2.5             0                                                    9        25.0            1                                                             2.5             0                                                    10       25.0            1                                                             2.5             0                                                    11       25.0            1                                                             2.5             0                                                    12       25.0            1                                                             2.5             0                                                    13       25.0            1                                                             2.5             1                                                    14       25.0            1                                                             2.5             0                                                    15       25.0            0                                                             2.5             1                                                    16       25.0            1                                                             2.5             0                                                    17       25.0            1                                                             2.5             0                                                    18       25.0            1                                                             2.5             0                                                    19       25.0            1                                                             2.5             0                                                    20       25.0            1                                                             2.5             0                                                    21       25.0            0                                                             2.5             0                                                    22       25.0            0                                                             2.5             0                                                    23       25.0            0                                                             2.5             0                                                    24       25.0            1                                                             2.5             0                                                    25       25.0            1                                                             2.5             0                                                    26       25.0            1                                                             2.5             1                                                    27       25.0            1                                                             2.5             0                                                    28       25.0            1                                                             2.5             0                                                    29       25.0            1                                                             2.5             0                                                    31       25.0            1                                                             2.5             0                                                    32       25.0            0                                                             2.5             0                                                    35       25.0            1                                                             2.5             0                                                    36       25.0            1                                                             2.5             1                                                    38       25.0            1                                                             2.5             0                                                    39       25.0            0                                                             2.5             0                                                    41       25.0            1                                                             2.5             0                                                    42       25.0            0                                                             2.5             0                                                    43       25.0            0                                                             2.5             0                                                    44       25.0            0                                                             2.5             0                                                    45       25.0            1                                                             2.5             0                                                    54       25.0            1                                                             2.5             0                                                    55       25.0            0                                                             2.5             0                                                    56       25.0            0                                                             2.5             0                                                    ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Wheatleaf Chlorophyll Retention - SI.sub.50 Values                                               Percent Chlorophyll                                                           Retained as                                                        Molar      Compared to Frozen                                         Cmpd No.                                                                              Conc.      Wheat Leaf Check                                                                              SI.sub.50                                  ______________________________________                                        2       10.sup.-4  72,65           5.0, 5.2                                           10.sup.-5  40,54                                                              10.sup.-6  11,5                                                       3       10.sup.-5  48              5.0                                                10.sup.-6  22                                                                 10.sup.-7  8                                                                  10.sup.-8  7                                                          4       10.sup.-4  54              5.2, 5.4                                           10.sup.-5  50,59                                                              10.sup.-6  16,10                                                              10.sup.-7  5                                                                  10.sup.-8  5                                                          5       10.sup.-5  74,67           5.2, 5.0                                           10.sup.-6  21,15                                                              10.sup.-7  12,13                                                              10.sup.-8  12                                                         7       10.sup.-5  68,69           5.4, 5.6                                           10.sup.-6  34,26                                                              10.sup.-7  13,13                                                              10.sup.-8  13                                                         9       10.sup.-4  67,68           5.5, 4.5                                           10.sup.-5  60,42                                                              10.sup.-6  18,29                                                      10      10.sup.-4  63              5.2                                                10.sup.-5  49                                                                 10.sup.-6  10                                                         13      10.sup.-4  58              5.6                                                10.sup.-5  61                                                                 10.sup.- 6 38                                                         14      10.sup.-4  78,66           5.0, 5.5                                           10.sup.-5  64,60                                                              10.sup.-6  26,23                                                      15      10.sup.-5  15              --                                                 10.sup.-6  7                                                                  10.sup.-7  8                                                                  10.sup.-8  8                                                          24      10.sup.-4  42,62           5.6, 5.4                                           10.sup.-5  54,53                                                              10.sup.-6  13,15                                                      25      10.sup.-4  56              5.1                                                10.sup.-5  48                                                                 10.sup.-6  19                                                         26      10.sup.-5  58              5.6                                                10.sup.-6  17                                                                 10.sup.-7  7                                                                  10.sup.-8  7                                                          27      10.sup.-4  64              5.0                                                10.sup.-5  45                                                                 10.sup.-6  7                                                          29      10.sup.-4  32              --                                                 10.sup.-5  24                                                                 10.sup.-6  8                                                          31      10.sup.-4  16              --                                                 10.sup.-5  12                                                                 10.sup.-6  19                                                         35      10.sup.-4  64              5.6                                                10.sup.-5  62                                                                 10.sup.-6  37                                                         36      10.sup.-5  70,89,56,56     6.7, 7.1,                                          10.sup.-6  59,80,54,34     6.3, 6.1                                           10.sup.-7  36,47,38,27                                                        10.sup.-8  11,22,20,30                                                38      10.sup.-4  54              4.1                                                10.sup.-5  30                                                                 10.sup.-6  16                                                         45      10.sup.-4  51              5.5                                                10.sup.-5  57                                                                 10.sup.-6  20                                                         Frozen Wheat Leaf Check                                                                      100                                                            Water Control  22                                                             ______________________________________                                    

                                      TABLE IV                                    __________________________________________________________________________    Leaf and Pod Senescence of Soybean Test Plants                                Treated at the Beginning Seed Stage                                                                                                 Days Senescence                                                               Delayed as                  Rate of                                                                             Leaf Senescence Ratings                                                                             Pod Senescence Rating Compared to the         Cmpd                                                                              Application                                                                         Days Post-Treatment   Days Post-Treatment   Untreated Check         No. (kg/ha)                                                                             20                                                                              21                                                                              22                                                                              28                                                                              29                                                                              31                                                                              34                                                                              35                                                                              36                                                                              42                                                                              43                                                                              20                                                                              21                                                                              22                                                                              28                                                                              29                                                                              31                                                                              34                                                                              35                                                                              36                                                                              42                                                                              43                                                                              Leaf                                                                              Pod                 __________________________________________________________________________    5   2.0       3.8 2.0 0.8     0.2   3.6 1.4 1.0     1.0                                                                             Not calculable              0.5       2.0 0.8 0.6     0.2   2.6 1.2 1.0     1.0                           0.125     2.6 1.6 0.8     0.4   2.6 1.4 1.0     1.0                       Untreated check                                                                             1.5 0.8                                                                               1.0     0.0   2.5 1.0 1.0     1.0                       7   2.0       3.2 1.8 0.6     0.2   2.8 1.0 1.0     1.0                                                                             16  2                       0.5       3.4 2.2 1.0     0.4   3.6 1.4 1.0     1.0                                                                             8    4                      0.125     3.0 1.8 0.8     0.2   3.0 1.2 1.0     1.0                       Untreated check                                                                             1.5 0.8 1.0     0.0   2.5 1.0 1.0     1.0                       7   2.0     3.0 2.0     0.8       3.0 1.8     1.0     7   3                       0.5     3.0 1.4     1.0       3.0 1.2     1.0                                 0.125   2.8 1.2     0.4       2.8 1.2     1.0                             Untreated check                                                                           2.2 1.4     0.8       2.6 1.0     1.0                             36  2.0   5.0     3.4     2.2 1.2                                                                             5.0     3.2     2.0 1.2                                                                             7   7                       0.5   4.2     1.6     1.2 0.6                                                                             4.0     1.6     1.2 1.0                           0.125 4.4     2.4     1.2 1.0                                                                             4.6     2.4     1.2 1.0                       Untreated check                                                                         4.0     1.8     1.0 0.6                                                                             4.2     1.6     1.2 1.0                       36  2.0     4.0     2.2 1.4 0.2   5.0     2.2 1.2 1.0 3   2                       0.5     4.2     2.2 1.0 0.0   5.0     2.0 1.0 1.0                             0.125   3.8     2.0 1.0 0.2   4.6     2.0 1.0 1.0                         Untreated check                                                                           3.8     1.6 1.0 0.0   4.6     1.8 1.0 1.0                         __________________________________________________________________________

I claim:
 1. Pyridinylurea N-oxide compounds of the formula: ##STR4## andacid addition salts thereof; wherein R is isopropyl, tert. butyl, orneopentyl; R¹ is hydrogen or methyl; each X independently is halogen,alkylI(C₁ -C₆), haloalkyl(C₁ -C₆), hydroxy, alkoxy(C₁ -C₆), 2-pyridinyl,alkyl(C₁ -C₆)thio or alkyl(C₁ -C₆)sulfonyl; A is 1 to 4; and wherein theNHCONRR¹ group is bonded to the pyridinyl ring in the 4-position. 2.Compounds of claim 1 wherein X is halogen, A is 1 or 2, and the halogenis in at least one of the 2- and 6-positions.
 3. Compounds of claim 1wherein R¹ is hydrogen, X is halogen and A is 1 or
 2. 4. A compound ofclaim 1 which is N-(2-chloro-4-pyridinyl-Noxide)-N'-(1-methylethyl)urea.
 5. A compound of claim 1 which isN-(2,6-dichloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)urea.
 6. A plantgrowth regulator composition comprising a plant regulating amount of acompound of claim 1 in admixture with an agriculturally acceptablecarrier or extender.
 7. A method of retarding senescence in soybeanplants which comprises applying to the plant or in the vicinity thereofa plant regulating amount of a compound of claim
 1. 8. A method ofretarding senescence in soybean plants which comprises applying to theplant or in the vicinity thereof a plant regulating amount of a compoundof claim
 2. 9. A method of retarding senescence in soybean plants whichcomprises applying to the plant or in the vicinity thereof a plantregulating amount of a compound of claim
 3. 10. A method of retardingsenescence in soybean plants which comprises applying to the plant or inthe vicinity thereof a plant regulating amount of a compound of claim 4.11. A method of retarding senescence in soybean plants which comprisesapplying to the plant or in the vicinity thereof a plant regulatingamount of the compound of claim
 5. 12. A plant growth regulatorcomposition comprising a plant regulating amount of a compound of claim1 in admixture with an agriculturally acceptable carrier or extender.13. A method of retarding senescence in soybean plants which comprisesapplying to the plant a plant regulating amount of a compound ofclaim
 1. 14. A plant regulatory compound of claim 1 selectedfrom:N-(2-chloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)ureaN-(2-chloro-4-pyridinyl-N oxide)-N'-(1,1-dimethylethyl)ureaN-(2-chloro-4-pyridinyl-N oxide)-N'-(2,2-dimethylpropyl)ureaN-(2-bromo-4-pyridinyl-N oxide)-N'-(1-methylethyl)ureaN-(2,6-dichloro-4-pyridinyl-N oxide)-N'-(1-methylethyl)ureaN-[2-(2-pyridinyl)-4-pyridinyl-N oxide]-N'-(1-methylethyl)ureaN-(2-chloro-4-pyridinyl-N oxide)-N'-methyl-N'-(1,1-dimethylethyl)ureaN-(2,6-dichloro-4-pyridinyl-N-oxide)-N'-(1,1-dimethylethyl)urea.
 15. Acompound of claim 1 which is N-(2-chloro-4-pyridinyl-Noxide)-N'-(1,1-dimethylethyl)urea.
 16. A compound of claim 1 which isN-(2-chloro-4-pyridinyl-N oxide)-N'-(2,2-dimethylpropyl)urea.